Write a program using three procedures.

The first should read text from the keyboard and store it in RAM.

The second should convert any upper case characters in the stored text to lower case.

The third should display the text on the VDU screen.

Modify the following for the above procedures:

; -------------------------------------------------------------- ; A program to read in a string of text and store it in RAM. ; The end of text will be labelled with ASCII code zero/null. ; -------------------------------------------------------------- ; THE MAIN PROGRAM MOV BL,70 ; [70] is the address where the text will ; be stored. The procedure uses this.

CALL 10 ; The procedure at [10] reads in text and ; places it starting from the address ; in BL.

; BL should still contain [70] here.

CALL 40 ; This procedure does nothing until you ; write it. It should display the text.

HALT ; DON'T USE END HERE BY MISTAKE. ; -------------------------------------------------------------- ; A PROCEDURE TO READ IN THE TEXT ORG 10 ; Code starts from address [10]

PUSH AL ; Save AL onto the stack PUSH BL ; Save BL onto the stack PUSHF ; Save the CPU flags onto the stack

Rep: IN 00 ; Input from port 00 (keyboard) CMP AL,0D ; Was key press the Enter key? JZ Stop ; If yes then jump to Stop MOV [BL],AL ; Copy keypress to RAM at position [BL] INC BL ; BL points to the next location. JMP Rep ; Jump back to get the next character

Stop: MOV AL,0 ; This is the NULL end marker MOV [BL],AL ; Copy NULL character to this position.

POPF ; Restore flags from the stack POP BL ; Restore BL from the stack POP AL ; Restore AL from the stack

RET ; Return from the procedure. ; -------------------------------------------------------------- ; A PROCEDURE TO DISPLAY TEXT ON THE SIMULATED SCREEN ORG 40 ; Code starts from address [10] ; **** YOU MUST FILL THIS GAP **** RET ; At present this procedure does ; nothing other than return.

; -------------------------------------------------------------- END ; It is correct to use END at the end.